The present invention relates to a golf ball having an excellent flight performance.
It is well-known that, in a golf ball, the high rebound of the ball itself and the air resistance-reducing effects during flight by dimples arranged on the ball's surface play important roles in enabling the ball to achieve a long carry when hit. A variety of methods have been devised for arranging dimples as densely and uniformly as possible on the surface of the ball so as to reduce air resistance.
The dimples ordinarily employed are depressions that are circular as viewed from above. Because such circular dimples are used, even if, in order to arrange the circular dimples to a high density, neighboring dimples are placed so closely to each other that the width of the land separating two dimples approaches zero, lands of a certain size having triangular or quadrangular shapes of a certain extent are formed in areas surrounded by three or four thusly arranged dimples. Also, because it is critical to arrange dimples as uniformly as possible on the spherical surface of the ball, some degree of compromise on the density of the arrangement of circular dimples has been required.
To arrange the dimples both uniformly and to a high density, dimple configurations have been adopted in which from two to ten types of dimples of differing diameter are arranged on the spherical surface of the ball in the manner of a regular octahedron or a regular icosahedron.
However, so long as only circular dimples are used, the practical upper limit in dimple surface coverage, defined as the total surface area of the dimples as a proportion of the total surface area of the sphere, is about 75% (which corresponds to a land surface coverage of about 25%).
Unlike the dimples described above, U.S. Pat. No. 6,290,615 discloses a golf ball in which projections that extend out on a lattice (lattice members) are disposed over a smooth spherical surface, partitioning the surface into hexagonal shaped bounded areas and thereby reducing the land area.
However, the hexagonal shaped bounded areas delineated by the lattice members lie on a spherical surface having a center that coincides with the center of the ball and are not dimples, thus having a poor air resistance lowering effect.